The main objective of this study is to assess the relative systemic bioavailability of diclofenac in the presence and absence of capsaicin by comparing the systemic bioavailability of diclofenac from a combination product (Diclofenac 2% + Capsaicin 0.075% Topical Gel) with two diclofenac only products, Diclofenac Mono Gel 2% and Voltarol® 12 Hour Emulgel 2.32% Gel, following topical administration.